1. Field of the Invention
The present invention generally relates to a method and apparatus for filling a display panel, and more particularly to a method and apparatus for filling a liquid crystal display (LCD) panel with liquid crystal material.
2. Description of the Related Art
Currently, many methods exist for filling liquid crystal display panels. However, such methods are extremely time-consuming, and thus the throughput is low for displays incorporating such liquid crystal panels.
Several attempts have been made to improve the speed, while maintaining cleanliness, with which the liquid crystal (LC) material filling process occurs. Recent improvements have been disclosed in the above-mentioned U.S. patent application Ser. No. 09/062,275, incorporated herein by reference. However, this method has drawbacks in that the application of edge pressure may give rise to cracking of the glass comprising the front and back faces of the panel.
Additionally, other conventional methods have attempted to increase the efficiency of the LC material filling process and LCD panel fabrication. However, these methods relating to displays (e.g., especially flat panel displays) still are problematic, and fail to provide a rapid liquid crystal filling process for the otherwise substantially completed panel.
Specifically, none of the conventional systems and methods provides for efficiently applying the liquid crystal between the plurality (e.g., two) of panel plates, enabling a uniform distribution of the liquid over the entire interior surface either prior to or after vacuum pump-down. Such a feature would allow for a rapid uniform distribution of the liquid crystal with minimum air entrapment and bubble formation (e.g., both of which are major concerns in the LCD fabrication art).
Furthermore, uniform distribution of the liquid obviates the need for substantial additional time for liquid diffusion or re-arrangement to provide the necessary smooth, continuous and uniform distribution of the liquid crystal medium within the panel.
Thus, with conventional methods, a large time period is required for the liquid crystal material to spread uniformly and continuously throughout the panel from individual droplets deposited onto the panel or by back pressure filling after pump-down with the two portions of the panel affixed to one another, and drawing in the liquid through a narrow channel from a liquid crystal reservoir.
For example, in one conventional method, at least one precision applicator or "micro syringe" is used as a delivery system for the liquid crystal material, for depositing an array of precisely spaced droplets onto a plate making up one half of an LCD panel. The droplet deposits are made at atmospheric pressure. However, filling is not performed within the vacuum chamber, thereby increasing the difficulty in handling and making the filling process more prone to contamination.
Additionally, the micro-syringe delivery system is very costly and cumbersome to operate, since the precision of the volume of each droplet required is such that if the total amount of liquid (e.g., by all of the micro-syringes) is off by even a small amount (e.g., 5%), the panel either will be partially collapsed or will be bulged outwardly after the two plates of the panel are joined. Moreover, this conventional method has no mechanism or method for bleeding off excess material. Thus, there is little, if any, margin of error for the total volume of the droplets deposited onto the panel plate. Further, the micro-syringe is expensive and requires extremely accurate calibration.
Other systems are known which pump out the panel, then place one partially opened edge in a trough of LC material, and expose the system to backfill pressure to fill the panel. This is a very complex, as well as very time-consuming, procedure.
Yet another disadvantage of the conventional systems is that some systems are unable to use both spacer beads and lithographically placed studs for providing a predetermined, uniform gap between the first and second panel plates of the display. Specifically, some conventional methods may only use either of the spacer beads or the lithographically placed studs.